I have a question related to the FAQ. Can one form _any_ linear
combination of any of the cell means from any cell means model ANOVA?
Having read a bit more it seems to be so. And I'm almost getting the
hang of posthoc testing via Stata's testanova framework.
Below I think I'm being silly and animal doesn't need to be in the cell
means table which makes things easier to follow from the online
examples.
For instance, if I have a split plot design,
within-subject factor
---------------------
stimulus1 stimulus2
drug animal1 cell 1 2
animal2 3 4
control animal3 5 6
animal4 7 8
This anova is: anova y drug/animal|drug stimulus drug*stimulus/,
repeated(stimulus).
I was interested in the following comparison of cells after finding a
drug*stimulus interaction significant:
((2-1)+(4-3)) / 2 = ((6-5)+(8-7)) / 2, average of differences between
stim1 and stim2 by group
This test would be equivalent to transforming the data to difference
scores (stimulus2-stimulus1), and then testing for a group difference
between drug and control groups. It's easy to do the latter, but I
wanted to know if test could do it directly and if the comparison I
want is an allowable test.
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